Rubber gloves are widely used for household uses, industrial uses in, for example, food industry and electronic part industry, and surgical and other medical uses. It is generally required for rubber gloves that (1) they have good softness of touch and are well-fitting and comfortable to wear, namely, they are capable of being easily stretched in conformity with movement of fingers so that fatigue does not itself felt even when they are worn for long hours, (2) they are not easily broken, namely, they have a high tensile strength, and (3) they exhibit good retention of close fittingness, namely, they are not easily slackened nor crumpled when fingers are moved, and they keep a well-fitted state for a long time.
Rubber gloves made by dip-forming natural rubber latex have widely been used, but, allergies to natural rubber sometimes cause rashes or itching due to protein contained in a slight amount in natural rubber.
Rubber gloves made by dip-forming a synthetic rubber latex, for example, an acrylonitrile-butadiene copolymer latex, are known. Allergy does not develop to rubber gloves made from an acrylonitrile-butadiene copolymer latex, but these gloves exhibit poor balance between the softness of touch or comfortable fittingness, and the tensile strength.
For example, U.S. Pat. No. 5,014,362 discloses gloves dip-formed from a composition comprising a carboxyl-modified acrylonitrile-butadiene copolymer latex having incorporated therein minor amounts of zinc oxide, sulfur and a vulcanization accelerator, which are characterized as exhibiting a tensile stress retention of almost zero % as expressed by the formula of (A/B)×100 wherein B is tensile stress as measured immediately after 100% elongation and A is tensile stress as measured when 6 minutes elapses from the measurement of B. These gloves are easily stretched, well-fitting and comfortable to wear, but their retention of close fittingness is poor.
International publication WO 97/48765 discloses gloves dip-formed from a composition comprising a carboxyl-modified acrylonitrile-butadiene copolymer latex, ammonium casein, sulfur and a vulcanization accelerator, and not containing zinc oxide. These gloves have high tensile strength, but they are not easily stretched and do not exhibit comfortable fittingness, and their retention of close fittingness is poor.
U.S. Pat. No. 5,910,533 discloses a dip-formed article made from a copolymer latex prepared by copolymerization of 80 to 99% by weight of a conjugated diene monomer, 0 to 10% by weight of an unsaturated acid monomer and 0 to 20% by weight of other unsaturated monomers such as acrylonitrile and methyl methacrylate. As a specific example of the copolymer latex, a copolymer latex comprised of 87 weight parts of butadiene, 10 parts of acrylonitrile and 3 weight parts of methacrylic acid is mentioned. Gloves made from this copolymer latex can easily be stretched, have good softness of touch and are comfortable to wear, but the tensile strength is low and they are liable to be broken during wearing.
International publication WO 00/21451 discloses gloves made by dip-forming a composition comprising an acrylonitrile-butadiene copolymer latex containing a specific amount of a carboxyl group, an extremely slight amount of zinc oxide, sulfur and a vulcanization accelerator, which are characterized as exhibiting a tensile stress retention in a range of 50 to 70%. These gloves exhibit good retention of close fittingness, but the balance between the softness of touch or comfortable fittingness and the tensile strength is occasionally poor.